2 Thessalonians 2:15

Therefore, brethren, stand fast
In the doctrine of the Gospel in general, and in the article of Christ's second coming in particular, and not in the least waver about the thing itself, nor be shaken in mind, and troubled as if it was just at hand; and the rather it became them to be concerned that they stood fast in the truth, and persevered unto the end, since there was to be a falling away, and the mystery of iniquity was already working, and antichrist would shortly appear, whose coming would be with all deceivableness, of unrighteousness; and they had the greater encouragement to continue firm and unmoved, seeing they were chosen from eternity unto salvation through sanctification and belief of the truth, and were called in time by the Gospel to the enjoyment of the glory of Christ in another world.

And hold the traditions which ye have been taught:
meaning the truths of the Gospel, which may be called traditions, because they are delivered from one to another; the Gospel was first delivered by God the Father to Jesus Christ, as Mediator, and by him to his apostles, and by them to the churches of Christ; whence it is called the form of doctrine delivered to them, and the faith once delivered to the saints: and also the ordinances of the Gospel which the apostles received from Christ, and as they received them faithfully delivered them, such as baptism and the Lord's supper; as well as rules of conduct and behaviour, both in the church, and in the world, even all the commandments of Christ, which he ordered his apostles to teach, and which they gave by him; see ( 2 Thessalonians 3:6 ) ( 1 Thessalonians 4:2 ) . And so the Syriac version here renders it, "the commandments": and these were such as these saints had been taught by the apostles, under the direction of Christ, and through the guidance of his Spirit; and were not the traditions of men or the rudiments of the world, but what they had received from Christ, through the hands of the apostles:

whether by word, or our epistle,
that is, by "our" word, as well as by our epistle, and so the Arabic version reads; these doctrines, ordinances, and rules of discipline were communicated to them, both by word of mouth, when the apostles were in person among them, and by writing afterwards to them; for what the apostles delivered in the ministry of the word to the churches, they sent them in writing, that they might be a standing rule of faith and practice; so that this does not in the least countenance the unwritten traditions of the Papists; and since these were what were taught them, "viva voce", and they received them from the mouth of the apostles, or by letters from them, or both, it became them to hold and retain them fast, and not let them go, either with respect to doctrine or practice.